The present invention relates to an implant for artificial teeth.
The invention is used particularly but not exclusively in the field of prosthodontics, where artificial teeth are fitted in the human jaw by inserting a metallic implant for each tooth in the jawbone and by fixing a corresponding artificial tooth therein.
Prostheses for artificial teeth are already known which use:
at least one artificial tooth support, which is designed to replace the root of the removed tooth and can be stably inserted in the jawbone at the region where the artificial tooth is to be applied, said support being generally made of titanium and being hollow (this support is commonly known as intrabony implant);
at least one structure for supporting an interchangeable artificial tooth with a tang for engagement in the recess of the tooth support (commonly known as stump).
The stump and the intrabony implant are coupled by fixing means which, in the current art, are mainly constituted by axial screw means whose drawback is that they are complicated and expensive as well as difficult to apply.
Furthermore, the screw coupling easily loosens due to the stresses produced by chewing and this can even lead to breakage of the threads, with possibly severe damage.
A solution to this problem, proposed by the same Applicant, is disclosed in Italian patent application UD 97 A 00084, which provides for an implantation system for artificial teeth of the type which provides for a hollow intrabony insert or implant to be inserted in a fixed manner in the jawbone and an artificial tooth assembly which has a stump associated with means for fixing in said insert.
According to this solution, in the cavity of the intrabony implant there are at least two annular ridges which are spaced and whose annular shape is interrupted so that the interruption is formed in one ridge in opposition to the interruption of the other ridge.
The stump also has a protrusion which enters and engages the cavity and has two lugs at the interruptions in order to pass beyond the ridges by axial insertion coupling and, by rotation, into corresponding underlying annular slots, engaging below them so as to prevent extraction.
In this manner, the problems are partially solved; in particular, greater safety against the danger of losing the artificial tooth is achieved.
Even this solution, however, is complicated and particularly expensive due to the provision of the double annular undercut acting as safety coupling with rotary insertion coupling, which is necessary in any case to avoid the danger of disengagement.
Such complexity is further increased by the limited size of the implants, also in view of the fact that the presence of the double undercut reduces the resisting cross-section, with the danger of failure.
Therefore, although the above solution is theoretically valid, it still entails a structure which is complicated and therefore, despite the higher safety that it provides, is expensive and therefore applicable only to users who can afford this higher cost.
Another drawback that occurs in conventional solutions is due to the fact that the annular thickness of the intrabony implant (outside diameter with respect to the cavity diameter) is necessarily reduced, since the outside diameter is limited by the thickness of the jawbone in the implantation area, and therefore there is the risk of excessively weakening the tang of the stump or the wall of the intrabony implant that accommodates the tang.
In any case, in view of the extremely intense stresses applied by the jaw during chewing, there is the danger that the former or the latter may break.
The aim of the present invention is, therefore, to eliminate the drawbacks noted above in conventional types, providing a new implant for artificial teeth in which the fixing means are even quicker and simpler than current ones yet are reliable and have low-production costs.
In accordance with the invention, there is provided an implant assembly, comprising: an intrabony implant which is designed to be inserted in a fixed manner in the jawbone and is provided with a cavity; an artificial tooth assembly with a tooth stump for the respective artificial tooth, said tooth stump having a lower stem to be inserted and fixed in said cavity of said intrabony implant, and a said tooth stump having an upper protrusion for engagement with an artificial tooth; which is characterized in that said cavity of said intrabony implant has an undercut annular recess below and above which there are hole portions having a smaller diameter, one of said hole portions, above said recess, being interrupted by at least one longitudinal access slot for the passage of at least one lug of the stem of said tooth stump by axial sliding and subsequent rotation of said stem in said recess, the outer upper end of said intrabony implant being polygonal, said tooth stump protruding above said lug with said protrusion having a polygonal region for the insertion of a polygonal annular bush for the mutual locking of said stump with respect to said intrabony implant so as to prevent rotation.